The present invention relates generally to data communications. More particularly, the present invention relates to a failover scheme for stackable network switches.
A stackable switch comprises a plurality of stack units. Like regular network switches, each stack unit comprises ports, a forwarding engine, and a control plane processor (CPP). But each stack unit also includes one or more stacking interfaces for interconnecting a plurality of the stack units via stacking links to form a stackable switch, in which one of the stack units is configured as the master stack unit. A stackable switch performs as a single large switch, with the control plane processor of the master stack unit acting as the control plane processor for the entire stackable switch.
In a stackable switch, a network interface can include ports on two or more of the stack units, for example by configuring the ports as a virtual local area network (VLAN). By definition, every network interface is assigned an Internet Protocol (IP) address. This configuration works well until the master stack unit can no longer communicate over the stacking links with one or more of the other stack units in the stackable switch, for example because one or more of the stack units, stacking interfaces, or stacking links has failed. When this happens, one or more of the stack units can communicate independently with the network using the same IP address, a network condition that is not permitted.